Process for imparting water repellency to cellulosic material comprising cellulosic fibers by reaction with an aerosol containing organo silicon halide



Feb. 25, 1958 E. ROBBART PROCESS FOR IMPARTING WATER REPELLENCY TO CELLULOSIC MATERIAL COMPRISING CELLULOSIC FIBERS BY REACTION WITH AN AEROSOL CONTAINING ORGANO SILICON HALIDES Filed Sept. 28, 1954 m m m8 mm V m Fig. 2

ATTORNEYS United States Patent C Edward Robbart, Cambridge, Mass.

Application September 28, 1954, Serial No. $58,785

'10 Claims. (Cl. 8-'-116) This invention relates to the treatment of cellulo'sic materials, particularly "materials comprising 'cellulosic fibers, such as cotton "fabrics, paper, fabrics containing fibers of regenerated cellulose (rayon) or cellulose esters '.(celltilose acetate or cellulose nitrate), and similar materials, and consists in a novel process of treating such materials with organo halogeno silanes (also known as organo silicon halides) to render them water repellent without seriously impairing the strength of the material or degrading its cellulosic constituents. In the treatment offabrics, the invention -is moreover, useful in stabilizing them against shrinkage and in imparting size.

Prior attempts to treat cellulosic fibers, such as paper, cotton goods and fabrics of regenerated cellulose or cellulose esters, with organo halogeno silanes have met with only limited success. Although therehas been little difficulty in rendering the fabrics water repellent, no process has heretofore been developed which does not result in serious degradation and loss of strength of the fabric, and none of the processes yet developed have, for this reason, met with commercial acceptance. '3 The present invention not only avoids the difficulties previously encountered tin efforts to utilize organo halogeno silanes in treating cellulosic materials, but in addilion, provides a process which may be "carried out continuously with the treatment being completely uniform over entire area of the material treated. 'To assure uniformity, in any case, 'it is desirable that every bit 'of material be treated under identical conditions, and that the silane be presented to the material at the rate it is used up in the treatment and at constant concentration, and this invention provides a sure and simple feature for accomplishing this result even though the rate of adding the silane to the treating apparatus be non-uni- ,In general, the process 'of this invention is practiced by exposing the cellulosic material to a gaseous mixture ofithe silane and an inert gas under time and temperature conditions found suitable for permitting the desired reaction between the material and :the shame while :avoiding the side reactions causing degradation, and immediatelyor very shortly" thereafter neutralizing the acidic reaction lay-products by immersing the material in a mild alkaline solution. The material is thereafter preferably 5 rinsed in water to remove excess alkali and salts and dried.

Preferably, the silane'is present in the gaseous mixture as an aerosol to assure constant saturation of the gaseous .phase with silane vapors, The liquid aerosol particles serve as "a reservoir supplyingsilane vapors to and throughout the gaseous phase as these vapors are removed by reaction with the material being treated. his is particularly advantageous in the continuoustreat- 7 mefnt; of' materials, since it assures constant and uniform inane vapor concentration "throughout the reaction chain-- '2 ber'while avoiding the necessity of carefully correlating the rate of adding silane with the rate the material is fed.

The time and temperature of the treatment are interdependent in accordance with Well known principles of chemical kinetics. At high temperatures, shorter exposures are required, since increased temperature not only increases the rate of reaction, but also increases the concentration of silane in the vapor phase, and at lower temperatures, the time of exposure may be considerably longer. Thus, if "the treatment is carried out at about 100 F., the time of exposure should be less than about 10-45 seconds, and preferably only a second or two, whereas at F. exposures as long as 2-6 minutes are generally-satisfactory, but "an exposure of from 1-60 seeonds is preferred. At F. the exposure may be as long as from 1-5 minutes, with exposures of from 1-30 seconds being preferred. Thus, within the normal room temperature range of about 70-100 -F. the maximum exposure time will vary generally between about 10 seconds and 6 minutes, and best results can generally be attained with exposure times of between about 1 second and l'minute.

In any treatment, it will be appreciated, the time of exposure will depend not only on the temperature, but also on the degree of water repellency desired, and, in the case of fabrics at least, also on the degree of size to be imparted and on the nature of the fiber, type of weave, etc. Another factor entering the selection of the proper'exposure time 'is the composition of the silane used in the process. Methyl chloro silanes, which are preferred, are commercially available as mixtures including such compounds as dimet'hyl dichloro silane (CH SiCl' methyl tri chlorosilane CH SiCl trimethyl chlorosilane (CH )SiCl, silicon tetrachloride SiCl and methyl dichlorosilane CH SiHCl As the components vary in volatility and in their reactivity toward the material treated, mixtures having higher concentration of the more volatile and/ or more reactive components demand shorter exposure time than mixtures less reactive or less volatile. The time and temperatures described, above have been found suitable for treatments with the commercially available methyl chloro silanes, such as Dri- Film sold'by the General Electric Company.

In general, organo 'halogeno silanes suitable for use in this invention include the methyl chloro silanes listed above, preferably those having two or more chlorine atoms, since they form polymeric chains of silicones when hydrolyzed. Cross-linked silicones are preferred to linear polymers and for. this reason it is desirable that the silane include some having three or four chlorine atoms, e. g. methyl 'trichlorosilane, silicon tetrachloride, or trichlorosilane (HSiCl or some methyl dichloro silane, which cross links through the valence bond of the hy- 5 drogen atom which is readily'removed, apparently by oxidation'or hydrolysis. In addition to the methyl chloro silanes, it is believed apparent that the corresponding ethyl and propyl compounds are also suitable, and that the bromo and fluoro compounds 'could also be used except for their expense and the dangerous nature of the latter. They are, however, known to react similarly to the chlorosilanes. This invention accordingly contemplates that other organo halogeno silanes may be used, particularly the lower alkyl silicon halides (e. 'g. methyl, ethyl, and propyl silicon halides).

Generally, the process is carried out using silane vapor mixedwith air, as by vaporizingsilane in a chamber and placing the material after equilibrati-ng in an atmosphere of between about 30 and relative humidity, in the chamber for the desired period of time, then rernoving it and further treating it to neutralize the reaction byw Actualfnnalysist.

the vapors iOf carbon tetrachloride; to an 'air-silanetmix ture, the explosion hazard is also reduced. 4

1 Informing the gaseous mixture ofthe silane andinert 1 gas, the former may be'incorp'or'ated in air or other'inert gas,1'but is preferably latomized to'produce anjiaerosol mixture'inthe form of a n'oticeabletog, or condensed to produce the" same result 'as' byg'c'oling a saturated a pH .ofbetween u7'and-ll Alkaline neutralizing agents particularly suitable include sodium carbonate,,sodium bi- V mildly basic aqueous solution,-preferably one-buffered at Q carbonate,gcalciumihydroxide, disodium phosphate, 'trisodium: phosphate, sodium acetate, andsimilar water- 7 soluble ibasic' compounds which form slightly basic aqueous solutionsof 'high'neu tralizing capacity. Strongly basic V t solutionsj epg gg ofpH higher than 11.0, are preferably avoided since'they tend toremove the silicone formed by the ,silane treatment. Dilute solutions of suchfstrongly basic'materials "as sodium hydroxide having a pH below 11 could be usedjbut the neutralizing capacity is quite low hecause'of'theextreme dilution; necessaryfor such low alkalinity. Ammonia'a'nd amines are alsopreferably avoided as neutralizing agents since their salts,- formed: 1

during neutralization, tend tobe retained on thecellulosic material'and cause gradual degradation: Thene'utralizing bath preferably also includes a' wetting agent efiective l to aid-,thejwetting of'the treated cellulose such" as a t nonionic'or' cationic wetting agent or others well-known to the art. f

After neutralization the material may then be rinsed f in water to remove residual salts and alkaline solution, and dried.

. The following examples describe in detail representa.- tive examples of methods for treatingmaterials according tothisinVentiQn, 'as it relates to the treatment of tfabricsw z s A-suitable container, forinstancea larger beaker, is supplied with an atmosphere of an aerosol ofa mixture "of methyl chloro silanes consisting'chiefiy of methyl trichloro silaneand dimethyl' dichloro silane (GEjDri? Film, sold by the General Electric Company, fschene'c utady New York), by atomizing the silane in'the c on tainer to..produce a noticeable fog'.-;The fabric, after equilibration ,in *an atmosphere of about-%,;relative humidity ,is exposed to the silane aerosol atmosphere in r the beaker, andis then removed and immersed in a warm 7 (e. g.,l00 F.)*concentrated aqueous'solution of sodium bicarbonate, containing a small amount ofa wetting agent :(eJg. 0.02% by. weight of an ordinary,nonionic wetting agent such a s'Triton X100, sold by ,Rohm 3S; I-Iaas Co Philadelphia,1Pa., and described as lan alkyl-"aryl poly ether alcohol). and is agitated therein. The fabric. is

' theirremoved,v rinsed. in Water and dried.

0iZ%'; miscellaneoiishigh boiling point inert resinousmate. r aand atomized into-aerosol-sizeparticles,i;

'j glanded by a rubber'strip 28 and passesup and do 7 through the chamber .around overhead.rollersjolson'ie of the paper is greatly increased; t 1, H

"A typical procedure'for continuously treatingf ricsm finally through a drier,'f

-drier,'(-not shown).f- I

A 7 Wm M V "x 1 4 2,824,778" A r i: products. Other inert gases are, however, entirely satis- 1 t,

1 factory, for instance, nitrogen and carbon dioxide which V have the advantage of eliminating anyexplosion hazard. Temp. of Time or Tensile j Also, in this'con nectioin, it has been foundt'hat-by adding' Example Treztfientv 9 igffiggg' assesses-ease.

droplets which werelreadily shed,tand'fromlable -l it;

will be seen that under' thejpreferred-hcondition; the

treated fabric has retained upwards'of 90% of its tensile strength. m j

Similar results may alsojbe attainedfjwith abricspf rayon, acetate and mixturesof these, withjfother fibers such as wool or nylon. j A Paper mayfalso be treatedin thi'simann i ffwith equally advantageous: results in being madewater repellent with? outserious'loss of strength. Moreover, the; wet strength j,

or paper by theproc'ess of this invention consists iri'adif vancingthei material through a' chamber in which culatedfan aerosol mixture of air and jthe silane i ferredapparatus for continuously carrying outi the process invention described in de a ha w th let-1 erence to the drawings in which: 1 .Fig. 1 is a plan view of the'apparatus, and. Fig..2 is a side elevation ofthe-apparatus.

each side wall and connecting with the row ofports'there in, and a section 20 "connecting the legs and extending around an end of ,the chamber. The 'connectinggsectio'n 20 houses a fan 22 in front; of which is a-sprayjinjector' 24- through which the silane is introduced ,UHQ'IOI'J/PICQUI-F The fabric 25 enters thechamberlg throu a aneutrali'zing tank 36 under" one or more 'dunlring'rolle'ri a 38;.theri through a similar rinsing tank (not showiflfaiud or instance, a standa'rd'itenter In operation, the atmosphere in the chamber lll isclrculated by the fan 2 2'whi1e the silane is introducedand 1 atomized in the air stream to provide an aerosol atrnos i phere within thegchamb'er The fabric, ZSQisQthen" run; through the chamber at a rateito provide the desired-Jere posure time; while additional'silane issupplied fronithe v spray; injector 24, to wrnaintain the aerosolatmosphere;

, As hasibeen pointed out;abovegiconstantprecisefei? relation of the rate, ofintroductionof silanei'wi'ththelrate 'of fabrictpassage is notnecessary, since the presence'of. V aerosol particles,assures'fcoiistant and unifo'rmgconcen tration of. the; silane vapor content oi"the,atmosphere saturation value; andthus assure'uniform treatmefit of the fabric.- The rate' of; supplying silane 'in'atypical opegaa;

tank and drier.

tion is 2% bylweight of the weight rate ogfahricj passag'ei 3 f r After the-fabric leaves the clhaniberyit'isirun' througli'q the neutralizingjbath 36; "conveniently;, a Warnisaturated,

aqueou'skolutioni'of sodiurh bicarbonate;, contajnig a i wetting agent; and is then rinsed and .dried in }the gees-res It 'is "not completely understood why fabrics treated in accordance with this invention are not impaired by aei'gradation or loss of strentgh, It is believed, however, that the silane reacts with surface moisture in the fabric and with free hydroxyl groups in the cellulosic fibers to form a water repellent surface coating accompanied by the liberation of a hydrogen halide, and that degradation is avoided by maintaining careful control over the timetemperature conditions during the exposure to the-silan'e and by complete and immedaite neutralization and removal of the acid reaction by-p ro'ducts.

A woven fabric consisting of about animal fibers and of about 70% of an approximately 50*50 mixture of viscose and acetate rayons was treated according to the process of this invention. Subsequent tests showed no loss of tonsil strength, an increase of about 15% in resistance to crease and wrinkle, and an abrasion resistance three times 'as great as that of the same fabric-conventionally finished, as well as high water repellency which was no more than slightly reduced by live washmgs.

This application is a continuation-in-part 'o'f'applicants copending application Serial No. 318,734, filed November 4, 1952, now U. S. Patent 2,782,090,

Having thus disclosed my invention and described in detail as representative thereof the best manner I have yet found of practicing it, I claim and desire to seizure by Letters Patent:

1. In the method of reacting organo silicon halides having as organo substituents alkyl groups with between one andthree'carbon atoms, with cellulosic material comprising cellulosic fibers reactive with said organo silicon halides to form a water repellent surface coating by contacting said material with said organo silicon halide in vapor form, the improvement of advancingsaid material continuously into contact with an atmosphere comprising an aerosol mixture of liquid particles of said organo silicon halide dispersed in an inert gas and maintaining a-constantly substantially saturated vapor phase of said organo silicon halide vapor adjacent to the surface of said material by supplying and maintaining dispersed liquid particles of said organo silicon halide in said atmosphere, maintaining said material in contact with said atmosphere until the organo silicon halide vapor reacts therewith and renders it water repellent, and continuously removing said material from said atmosphere.

2. In the method of reacting organo silicon halides having as organo substituents alkyl groups with between one and three carbon atoms, with cellulosic material comprising cellulosic fibers reactive with said organo silicon halides to form a water repellent surface coating with the liberation of free hydrogen halide by contacting said material with said organo silicon halide in vapor form, the improvement of advancing said material continuously into contact with an atmosphere comprising an aerosol mixture of liquid particles of said organo silicon halide dispersed in an inert gas, and maintaining a constantly substantially saturated vapor phase of said organo silicon halide vapor adjacent to the surface of said material by supplying and maintaining dispersed liquid particles of said organo silicon halide in said atmosphere, maintaining said material in contact with said atmosphere until the organo silicon halide vapor reacts therewith and renders it water repellent, continuously removing said material from said atmosphere, and removing the liberated hydrogen halide from the material.

3. In the method of reacting organo silicon halides having as organo substituents alkyl groups with between one and three carbon atoms, with cellulosic fibrous sheet material reactive with said organo silicon halides to form a water repellent surface coating with the liberation of free hydrogen halide by contacting said material with said organo silicon halide in vapor form, the improvement of advancing said material continuously into contact with an atmosphere comprising an aerosol mixture or liquid particles "of :said "organo silicon halide dispersed in an inert gas and maintaining aconstantly substantially saturated vapor phase of said organo silicon halide vapor adjacent to the surface of said material by supplying and maintaining dispersed liquid particles of said organo silicon halide in said atmosphere, maintaining said material in contact with said atmosphere until the organo silicon halide vapor reacts therewith and renders it water repellent, continuously removing said material from said atmosphere, and finally neutralizing and removing hydro gen halide by contacting the material with a basic aque ous solution having a pH between? and '11. a

'4. In the method of reacting organo *siliconfiha'lides selected from the group consisting of: methyl etrichlorm silane; dimethyl dichlorosilane; methyl dichlorosil'ahe; trimethyl chlorosilane; and mixtures of the foregoing silanes, with cellulosic material comprising cellulosic reactive wtih said organo silicon halides to form a water repellent surface coating by 'contacting said material with said organo silicon halide in vapor form, the improvement 'of advancing said material continuously into contact with an atmosphere comprising anaerosol mixture of liquid particles of 'sai'd'organo silicon halide dispersed in an inert gas and maintaining a constantly substantially saturated vapor phase of said organo silicon halide vapor adjacent to the surface of said material by supplying and maintaining dispersed liquid particles of said organo :silicon halide in said atmosphere, maintaining said material in contact with said atmosphere until the-organo silicon halide vapor reacts therewith and "renders it water repel lent, and continuously removing said material from said atmosphere.

5. In the method of reacting -organo silicon halides selected from the group consisting of-(methyl "trichlorosilane; dimethyl dichlorosilane; methyl dichlorosilane;itri methyl chlorosilane; and mixtures of the foregoing :silanes, with cellulosic fib'rous sheet material reactive "with said organo silicon halides 'to form a water repellent :sur-

face coating with the liberation of free hydrogen chloride by contacting said material with said organo silicon halide in vapor form, the improvement of advancing said material continuously into contact with an atmosphere comprising an aerosol mixture of liquid particles of said organo silicon halide dispersed in an inert gas and maintaining a constantly substantially saturated vapor phase of said organo silicon halide vapor adjacent to the surface of said material by supplying and maintaining dis persed liquid particles of said organo silicon halide in said atmosphere, maintaining said material in contact with said atmosphere until the organo silicon halide vapor reacts therewith and renders it water repellent, continuously removing said material from said atmosphere, and finally neutralizing and removing hydrogen chloride by contacting the material with a basic aqueous solution having a pH between 7 and 11.

6. The process defined by claim 5 wherein the material is exposed to the atmosphere at a temperature of less than about F. and for a time of not more than about six minutes.

7. In the method of reacting organo silicon halides having as organo substituents alkyl groups with between one and three carbon atoms, with a fabric comprising cellulosic fibers reactive with said organo silicon halides to form a water repellent surface coating with the liberation of free hydrogen halide by contacting said fabric with said organo silicon halide in vapor form, the improvement of advancing said fabric continuously into contact with an atmosphere comprising an aerosol mixture of liquid particles of said organo silicon halide dispersed in an inert gas and maintaining a constantly substantially saturated vapor phase of said organo silicon halide vapor adjacent to the surface of said fabric by supplying and maintaining dispersed liquid particles of said organo silicon halide in said atmosphere, maintaining said fabric in contact with said atmosphere until the V I organo siliconjhalidewapor reacts therewithand renders it water repellent, continuously removing said fabric from said atmosphere, and removing. the liberated hydrogen halide from said fabric. i a 1 8. In the method of reacting organo silicon halides a 18' a t halide vapon'adjacent tothe surface of said paper by supplying and maintaining dispersed liquid particles of said organo silicon halide'in said atmosphere, maintaining said paper in contact with said atmosphere untilthe selected from thegroup 'consisting of: methyl 'trichlorosilane; dimethyl dichlorosilane; methyl dichlorosilane;

trimethy'l chlorosilane; and mixtures of the ,foregoing silanes, with"a fabric comprising ce'llulosic fibers reactive with said organo silicon halides to form a water repellent surface coating with the liberation of free hydrogen chloride by contacting said fabric with said organo silicon halide in vapor'form; the improvement of advancing said fabric continuouslyiinto contactwith'an atmosphere corn prising an aerosol mixture of liquid particles of said organo silicon halide dispersed in an inert gas and main 'taining a constantly substantially saturated vapor phase 7 "of said organo silicon halide. vapor adjacent to the surface of 'said fabric by: supplying and maintaining dispersed liquid particles of said organo silicon halide ,in' saidatmosphere, maintaining said fabric in contact with a said atmosphereh'until the Lorgano siliconfhalide vapor 're'acts therewith and renders it water repellent, continu- 1ously removing said fabric from said atmosphere, neutral-,

izing and removing hydrogen chloride'by contacting the fabric with a basic aqueous solution haying a pH between 7and1 l. a l a,

'9. In the method' jof, reacting organo, silicon halides having as 'organ o substituents alkyl groupsj'with between one and three carbonatomgwith paper comprising cellulosica fibers reactive'fwithrsaid organo silicon halides to form a water repellent surface coatingby contacting said paper withsaid forgano' silicon 'halide' in vapor form, the improvementof'advancing said paper continuously into contact with an'atmosphere comprising anjaerosol mixrture of liquid particles of said organo silicon halide msorgano'silicon halide'vapor reacts therewith and renders it water repellent, and continuously removing said paper from said atmosphere,

7 10. In the method of reacting organo silicon halides having as organo substituents' allgyl groups with between one and three carbon atoms,lwi th paper comprising cellu losic fibers reactive with said organo silicon halides to form a water repellent surface coating with the liberationf of'free hydrogen'halide by contacting said paper with said organo silicon halide in vapor form; thefimprovement of advancing said paper continuously into contactwith an atmosphere comprising an aerosol mixture of' liquid particles of'said organo silicon halide dispersed;

persed in ,an inert gas and maintaining a constantly'suba stantially; saturated vapor phase of said organo silicon in an inert gas and'm'ain'taining a constantly substan tially saturated vapor phase of said'or'gano silicon halide l a vapor adjacent to the surfaceof said paper by supplying and maintaining dispersed liquid ,particles'lof said organo :7 silicon halide in said atmosphere, maintaining said paper in contactlwith said atmosphere until the organosilicon halide vapor reacts therewith and renders it water repellent, continuously removing said paper from :said atmosphere, and. removing the liberated hydrogen halide 'UNITED STATES PATENTS References Cited the, file of this patent I 2,639,213' Barth May19, 195 3- I I, V FOREIGN PATENTS a 1 465,257 Canada May 23, 19 50 

1. IN THE METHOD OF REACTING ORGANO SILICON HALIDES HAVING AS ORGANO SUBSTITUENTS ALKYL GROUPS WITH BETWEEN ONE AND THREE CARBON ATOMS, WITH CELLULOSIC MATERIAL COMPRISING CELLULOSIC FIBERS REACTIVE WITH SAID ORGANO SILICON HALIDES TO FORM A WATER REPELLENT SURFACE COATING BY CONTACTING SAID MATERIAL WITH SAID ORGANO SILICON HALIDE IN VAPOR FORM, THE IMPROVEMENT OF ADVANCING SAID MATERIAL CONTINUOUSLY INTO CONTACT WITH AN ATMOSPHERIC COMPRISING AN AEROSOL MIXTURE OF LIQUID PARTICLES OF SAID ORGANO SILICON HALIDE DISPERSED IN AN INER GAS AND MAINTAINING A CONSTANTLY SUBSTANTIALLY SATURATED VAPOR PHASE OF SAID ORGANO SILICON HALIDE VAPOR ADJACENT TO THE SURFACE OF SAID MATERIAL BY SUPPLYING AND MAINTAINING DISPERSED LIQUID PARTICLES OF SAID ORGANO SILICON HALIDE IN SAID ATMOSPHERE, MAINTAINING SAID MATERIAL IN CONTACT WITH SAID ATMOSPHERE UNTIL THE ORGANO SILICON HALIDE VAPOR REACTS THEREWITH AND RENDERS IT WATER REPELLENT, AND CONTINUOSLY REMOVING SAID MATERIAL FROM SAID ATMOSPHERE. 